1. Field of the Invention
This invention generally relates to fluorinated and nonfluorinated block copolymer and composition formed therefrom useful for coating an implantable device such as a drug eluting stent.
2. Description of the Background
Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents are used not only for mechanical intervention but also as vehicles for providing biological therapy. To effect a controlled delivery of an active agent in stent medication, the stent can be coated with a biocompatible polymeric coating. The biocompatible polymeric coating can function either as a permeable layer or a carrier to allow a controlled delivery of the agent.
Fluorinated polymers, such as poly(vinylidene fluoride-co-hexafluoropropylene), have been used to form drug-eluting stent (DES) coatings and can effectively control the release of pharmaceutical agents from a stent. DES coatings formed of these fluorinated polymers also have excellent mechanical properties and are biocompatible and biologically inert. However, polymers of fluorinated olefins are very hydrophobic and may have low glass transition temperatures. Too high a hydrophobicity of the polymeric coating on a DES often reduces the permeability of the coating and thus slows down the release rate of a drug on the coating to an undesirable level.
The polymer and methods of making the polymer disclosed herein address the above described problems.